Document stacker apparatus

ABSTRACT

Document stacker apparatus wherein transport belts are continuously in contact with documents as they are transported to a stacking bin. At the stacking bin, roller means forces the trailing edge of the document downwards so that it does not interfere with the leading edge of a succeeding document.

United States Patent [191 Stephenson DOCUMENT STACKER APPARATUS Paul A. Stephenson, Farmington,

[75] Inventor:

Conn.

[73] Assignee: Xerox Corporation, Rochester, [22] Filed: May 12, 1969 I 21 Appl. No.: 823,865

[52] U.S. C1. ..271/64, 271/68, 271/76 [51 Int. Cl. ..B65h 29/58 I [58] Field of Search ..271/64, 65, 88, 76, 271/68 [56] References Cited UNITED STATES PATENTS 3,047,288 7/1962 Ramm ..271/65. X 3,224,761 12/1965 Meyer-Jagenberg.... ..271/68 3,430,950 3/1969 Marsh et a1 ..271/64 10/1950 Peyretrune ..271/88 3,395,916 8/1968 Dobson et a1. ..271/88 FOREIGN PATENTS OR APPLICATIONS 1,081,832 5/ 1 960 Germany ..271/64 1,108,614 6/1961 4 Germany.... 1,223,681 8/1966 Germany ..271/88 Primary ExaminerEvon C. Blunk Assistant Examiner-Douglas D. Watts Attorney-James J. Ralabate, Irving Keschner and John E. Beck [57] ABSTRACT Document stacker apparatus wherein transport belts are continuously in contact with documents as they are transported to a stacking bin. At the stacking bin, roller means forces the trailing edge of the document downwards so that it does not interfere with the leading edge of a succeeding document.

1 Claim, 3 Drawing Figures Patented April 24, 1973 3 Sheets-Sheet l 225:3: @2550 25 L 5555 mm QM 22.2592. v) 4 1553555 I L[ 555w 3mm 8 9 m\\ l 060 w BFEQQ mm 555w mm w? vw 063 R 405.28 mm EFSQEEEE 5 INVENTOR PAUL A. STEPHENSON gYJr gwa g ATTORNEY Patented April 24, 19 73 3,729,188

3 Sheets-Sheet 5 DOCUMENT STACKER APPARATUS BACKGROUND OF THE INVENTION In recording apparatus of the type that record the output of electronic computers, telemetering receivers and the like, high operating speed is critically important because of the high rate with which data for printing is produced by such equipment. As the speed of recording the output of such equipment on a recording medium is increased, the problem of handling the recording medium after data is printed thereon becomes-acute as the recording speed increases, particularly for extremely light weight recording mediums. The usual handling steps involved after the data is printed is to cut the recording medium into appropriate lengths i.e. corresponding to a book page, and then transporting the cut medium, or documents, to an appropriate stacking system. A critical problem associated with stacking flexible sheets or documents transported at high speeds is to prevent the trailing edge of a sheet from interferring with the leading edge of the succeeding sheet, thereby preventing the succeeding sheet from bending, being deformed or even jamming the stacking system. Prior arrangements for overcoming this problem have included techniques for providing positive control of both edges of each document by mechanically engaging both ends thereof, by utilizing vacuum forces to maintain the document in contact with a moving conveyor, and by electrostatically tacking the documents to a transport belt. Each of the aforementioned prior art arrangements have disadvantages associated therewith. For example, in order to mechanically engage both edges of a document, additional mechanical elements are introduced into the system which may add to the possibility of a malfunction. The vacuum systems have undesirable aspects in performance. In xerographic apparatus, for example, if a document is placed under the influence of a vacuum suction originating along the longitudinal spaces between the transport belts and parallel to the direction of movement, the document will maintain its relation to the sources of suction throughout its advancement along the transport path. This means that if a crinkled onionskin document is conveyed and its crinkles are parallel to the areas of suction, the crinkles will be preserved while the document, as a whole, is flat with the moving belts. If the crinkles are significant, then those crinkled areas existing between sources of suction may be outside the depth of field of a lens system which focuses the document image onto a lightsensitive receptor, thereby distorting the copies. In order to electrostatically tack documents to a transport belt, a electrostatic tacking device, such as a conventional corotron, is obviously required. Once the documents reach the stacking. area, additional apparatus is required to strip the tacked documents from the transport belt.

SUMMARY OF THE INVENTION The present invention relates to improved stacking apparatus and in particular, stacking apparatus which stacks documents at very high speeds. The documents are transported to a stacking bin by a belt transport system wherein the documents are continuously in contact with the belt. As the document approaches the stacking bin, a roller adjacent thereto forces the trailing edge of the document downward onto the stack,

thereby preventing the trailing edge thereof from interferring with the leading edge of a succeeding document.

It is an object of the invention to provide a novel, high speed document stacking apparatus.

It is a further object of the present invention to provide a high speed stacking apparatus wherein the trailing edge of document does not interfere with the leading edge of a succeeding document.

It is still a further object of the present invention to provide a novel stacking apparatus wherein the stack is maintained at a uniform height and wherein the document is conveyed to a stacker back plate whereat thedd'cument is squared thereagainst and held until another document is stacked thereover.

DESCRIPTION OF THE DRAWINGS For a better understanding of the invention as well as other objects and further features thereof reference is made to the following detailed description which is to be read in conjunction with the accompanying drawings wherein:

FIG. 1 is a block diagram of a system wherein the novel stacker apparatus of the present invention may be utilized;

FIG. 2 is a diagramatic plan view of the stacker apparatus of the present invention; and

FIG. 3 is a diagrammatic plan view of another embodiment of the novel stacker apparatus.

DESCRIPTION OF THE PREFERRED" EMBODIMENTS Referring now to FIG. I, there is shown a schematic block diagram illustrating the system environment in which the novel stacker apparatus of the present invention may be utilized. In fact, however, the stacker of this invention may be used for high speed stacking of virtually any type of cut sheets which can be fed through it. A printer unit 10 receives coded input information from a data transmission systemQsuch as a digital computer, and translates the computer output information into hard, or permanent, documents. The documents are cut to a desired lerigth by a cutter system, illustrated in FIG. 1 as part of the printer unit 10. The printer unit 10 may include a cathode ray tube coupled to the output of the digital computer for displaying the output thereof. The cathode ray tube output may be made permanent by projecting the displayed output onto a electrostatically charged photosensitive medium which is then developed and transferred to a recording medium according to known xerographic techniques. The recording medium is cut into documents, or sheets, 12 and are transported on belt 14 to the novel stacker apparatus 16 of the present invention which will be described in more cletail hereinafter with reference to FIGS. 2 and 3. The various printing and cutting operations are controlled by printer/cutter control logic 18 which transmits command signals via lead 20 to the printer unit 10. The stacker apparatus 16 is controlled by stacker control logic 22. The printer/cutter control logic l8 and the.

stacker control logic 22 interact via signals on leads 24 and 26 to control the operation of the system. The output from the stacker control logic 22 controls a stacker gate within stacker apparatus 16 via a signal generated on lead 28,. the stacker gate diverting the documents into predetermined stacking bins as will be described hereinafter. A stacker tray driving mechanism 30, the output of which drives stacking trays within stacker apparatus 16, is controlled via a signal on lead 32. The stacking tray position within stacker apparatus 16is monitored by a plurality of switches mounted to stacker apparatus 16, the signals appearing at the output of the switches being transmitted to the stacker control logic 22 via lead 34.

Referring now to FIG. 2, there is shown a diagramatic plan view of stacker apparatus 16. The documents are transported via transport belt 14 to stacking device 16 as shown in FIG. 1. With member 134 in the position shown, the documents are transported by belt 52 to a guide member, such as a baffle 54, and are guided thereby to the entrance 56 of a stacker unit indicated generally by reference numeral 60. Transport belts 62 and 64 engage each document 12 as it reaches entrance 56 and the document is transported thereby to stacker bin 96. Driver roller 66, energized by motor 67, drives belt 62 around guiderollers 68, 70 and 72.

v The guide rollers are arranged so that belt portion 62' guides the documents so that they enter the stack at an angle to the top of the stack 13. The continuous positive influence of belt portion 62' on each document entering the stack 13 prevents interleaving and jamming and enables the documents to be handledgently, with little curling or warping. The belt portion 62 transports the documents as they enter stacker bin 96 against stacker back plate 80, squaring the documents thereagainst as the stack is formed. As the documents are transported to stacker back plate 80 which acts to retain the documents in stacker bin 96 and form stack 13, roller 70 acts to force, or snap, the trailing edge of each document 12 down on the top of the stack 13,

thereby keeping the trailing edge thereof from interfering with the leading edge of a succeeding document. The angle 0 at which each document enters stack 13, such that the entering document strikes the stack away from the trailing edge thereof, is effective to prevent the trailing edge of the document on top of the stack from interfering with the leading edge of the entering document, thereby preventing a jam in the document transport system. It should be notedthat belt portion 62' is preferably maintained in contact with the top of the stack 13, since the action of roller 70 in forcing the trailing edge of each entering document shown on the stack is enhanced thereby.

Aplurality of magnetic reed switches 84 and 88 may be mounted to the inside edge of stacking bin 96 for locating the position of a stacking tray 98, which, in combination withback plate 80, forms stack 13. The

backplate 80 may comprise movable guides so that varying document lengths may be stacked properly. The stacking tray 98 is movably mounted within the stacking bin 96. Mounted to one end of tray 98 is a magnet 100,. the magnet shunting the magnetic reed switches as the tray traverses the stacking bin 96 inthe direction indicated by arrow 102. The switches indicate the position of tray-98 and when they are shunted by magnet 100, the switches are closed. When the switches are closed electrical signals appear at the output leads thereof and are coupled to the stacker control logic 22 via OR gate and lead 34. The control logic unit 22, in response to the signals fed thereto by the switches, controls the stacker tray driving mechanism 30 via a control signal generated on lead 32. As shown in FIG. 2, the stacking tray driving mechanism comprises a slow speed motor 110, the output shaft 112 thereof being coupled to the input hub of clutch 114. The output hub of clutch 114 is coupled to the driving shaft 115 of motor 116. Shaft 115 is connected to a gearing mechanism 118 which couples the shaft to a driving mechanism 120, which may comprise, for example,.a chain 122 driven around pulleys 124 and 126. The tray 98 is mounted to the driving chain 122 via connecting means 128.

Means are provided for controlling the height of stack 13 so that the stacker presents a common face to all documents. A microswitch 83 may be provided to detect the change in the stack height. The buildup of the. stack height occurs as documents are added to the stack 139A pivotable extension 86 is rotated when the document stack reaches a pre-determined level, causing switch 83 to close, thereby signalling control logic unit22 via gate 85 and lead 34. In response thereto, control logic unit 22 generates signals on leads 32a and 32b to energize the slow speed motor and engage clutch 114, respectively, thereby drivingshaft of motor 116. Shaft 115 rotates in a direction such that gearing mechanism 118 and chain 122 drives tray 98 a predetermined distance downwards, thereby lowering stack tray 98 until pivotable extension 86 returns to its initial position, thereby opening switch 83 and deenergizing motor 110 and disengaging clutch 114. The slow speed motor 110 is not continuously engaged but is periodically indexed downward to maintain a constant stack level. An alternate technique which may be utilized to control the height of stack 13 is described in U.S. Pat. No. 3,301,126. Photoelectric apparatus also may be utilized to detect and then control the height of the stack.

The magnetic reed switches'control the position of tray 98 in the following manner. Reed switch 84 may be positioned to correspond to a stacker full condition. Therefore, when tray 98 reaches a position such that magnet 100 shunts switch 84, a signal is generated at the output thereof and coupled to stacker control unit 22 via gate 85 and lead 34. Control logic unit 22, in response thereto, generates a control signal on lead 28 which actuates a solenoid 130. Solenoid is coupled to a member 132 having a finger-like extension 134. The actuation of solenoid 130 causes extension 134 to be interposed in the path of the documents being transported on belt 14. The documents 12 .are thereby guided to a document stacker unit by extension 134 and baffle 142 to be stacked in stacking bin 146 in an identical manner as described with reference to stacker 60. The description of stacker unit 140 will, therefore, be omitted to avoid redundancy. When the tray 98 reaches a position such that magnet 100 shunts reed switch 88, corresponding, for example, to the ultimate stop level of the tray 98 a signalis transmitted to control logic unit 22 via gate 85 and lead 34. The control logic unit 22, in response thereto, generates a signal only on lead 32c, thereby energizing motor 116 while the absence of a signal on lead 32b maintains clutch 114 disengaged. The rotational speed of shaft 115 when motor 116 is energized is greater than that when motor 110 is energized and clutch 114 is engaged, as previously described and rotates shaft 115 rapidly in a direction opposite to that when driven by motor 110. Gearing mechanism 118 and chain 122 drives tray 98 in an upwards direction to an initial position in preparation for another stacking cycle. It should be noted that additional switches may be located along the stacker bins to provide'additional control functions for the stacker units.

The system as described hereinabove enables documents or sheets of paper of various lengths to be stacked uniformly in stacking bins at high speeds. Documents traveling at speeds greater than 45 inches per second have been successfully stacked. To illustrate the stacking speed capabilities of the present invention, documents three inches long traveling at 45 inches per second can be stacked at a rate greater than 50,000 documents per hour. The stacking system as described hereinabove has been utilized when the document leave the printer unit face down, the documents being stacked face down in bins 96 and 146. The term face down is herein defined to mean that the face of the document upon which an electrostatic latent image has been developed is delivered to the stacker transport system or to the stacking bins such that the developed face is positioned facing towards belt 14 while the term face up is defined to mean that developed documentface is positioned facing away from belt 14. If documents emerge from printer unit 10 face up and it is desired to collate the documents in an ordered sequence in both stacker bins, a modification of the system described in FIG. 2 is necessary.

As shown in FIG. 3, the stacker units for stacking documents emerging face up from the printer unit 10 are indicated generally by reference numerals 150 and 170. The documents enter transport belts 152 and 172 with the developed side face up, and are transported to member 154 having a guide finger 156 thereon. The finger 156 guides the documents into a receiving area formed by belts 152 and 158. The documents are inverted and transported to stacking bin 160 and stacked as described hereinabove with reference to FIG. 2, belt portion 152' conveying the documents to back plate 162 and roller 164 forcing down the trailing edge thereof, preventing interference with the leading edge of a succeeding document. When stacking bin 160 is full, solenoid 166 is disengaged, rotating guide finger 156 away from the transport path of the documents so that they are transported to entrance area 168 of stacking unit 170, wherein the documents are stacked and inverted as described previously. The apparatus of FIG. 3 also performs an additional function other than collating. When the documents emerge face up from printer l0 and if they are not inverted; the documents are transported to the stacking bins face up, as described hereinabove with reference to FIG. 2. If the documents have been developed'with toner containing a thermally softenable resin, such as utilized in the xerographic process, toner which has not been totally fused, perhaps due to faulty fusing may be rubbed off when the document is stopped by the back plate 162.

'It should be noted that a combination of the document stacker described in FIG. 2 and the inverting document stacker shown in FIG. 3 may also be utilized.

Although document stackers of varying degrees of complexity are well known in the art, the invention described hereinabove provides novel, simple, economical and efficient apparatus for stacking documents at very high speeds. The belt transport system described provides a positive, continuous control over the documents as they enter the stacking area, the control continuing even as the documents enter the stacking bins. This type of positive control substantially reduces the possibility of jamming of the documents as they are transported at high speeds to the stacking bins and also holds each document against a stop member in the bin on top of the stack until a succeeding document is stacked thereupon. This latter result enables the stack to be squared against the stop member and prevents a light weight document entering-the stack from fluttering down on top of the stack, with the attendant reduction of stacking speed and possibility of jamming. The action of the guide roller in forcing the trailing edge of a document entering the stack down on top of the stack, thereby preventing the trailing edge of the document from interfering with the leading edge of a succeeding document, provides an additional technique for substantially reducing the possibility of malfunction in the document stacker apparatus.

What is claimed is: 1. Apparatus for stacking documents comprising: a transport system for transporting documents along a transport path to a first stacking bin, said bin including a stacking tray to form a first stack thereon, said transport system comprising a transport belt having a first sloped section for engaging documents delivered thereto and transporting said document to said stack, said documents entering said first stack at an angle thereto, said transport belt having a second section substantially parallel to and in contact with the top of said first stack for engaging documents entering said stack, said documents being under the positive and continuous control of said transport belt, means adjacent said first and second belt sections for applying a force to each document entering said first stack whereby the trailing edge of each document is forced down on top of said first stack, means for stopping said documents as they are transported to said first stack by said second belt section, said documents being held against said stopping means by said second belt section until a succeeding document enters said first stack, means for controlling the height of said first stack,

and means for directing said documents to a second stacking bin when said first stack contains a predetermined number of documents, wherein said documents are delivered to said transport system face up, said transport system being arranged to invert said face up documents whereby said documents are stacked face down in said first and second stacking bins. 

1. Apparatus for stacking documents comprising: a transport system for transporting documents along a transport path to a first stacking bin, said bin including a stacking tray to form a first stack thereon, said transport system comprising a transport belt having a first sloped section for engaging documents delivered thereto and transporting said document to said stack, said documents entering said first stack at an angle thereto, said transport belt having a second section substantially parallel to and in contact with the top of said first stack for engaging documents entering said stack, said documents being under the positive and continuous control of said transport belt, means adjacent said first and second belt sections for applying a force to each document entering said first stack whereby the trailing edge of each document is forced down on top of said first stack, means for stopping said documents as they are transported to said first stack by said second belt section, said documents being held against said stopping means by said second belt section until a succeeding document enters said first stack, means for controlling the height of said first stack, and means for directing said documents to a second stacking bin when said first stack contains a predetermined number of documents, wherein said documents are delivered to said transport system face up, said transport system being arranged to invert said face up documents whereby said documents are stacked face down in said first and second stacking bins. 